Two medicines, side by side
Metronidazole vs cephalexin
Metronidazole and cephalexin are both labeled for bacterial infections. Drugs@FDA records approvals of metronidazole since 1963 and of cephalexin since 1971. Pharmacies paid $0.102 per metronidazole 250 mg tablet and $0.120 per cephalexin 500 mg capsule (NADAC, October 7, 2026); the strengths differ, so the two prices are not like for like. Metronidazole's other strengths are brand-only: $2.60 per mL (Likmez 500 mg/5 mL suspension). In FDA's classes, metronidazole is a nitroimidazole antimicrobial and cephalexin a cephalosporin antibacterial.
Check it at the source: the metronidazole FDA label on DailyMed (effective September 3, 2024); the cephalexin FDA label on DailyMed (effective December 31, 2020).
Highlights of the metronidazole record
Metronidazole (Flagyl) · label of September 3, 2024
Metronidazole has been shown to be carcinogenic in mice and rats (see PRECAUTIONS ). Unnecessary use of the drug should be avoided. Its use should be reserved for the conditions described in the INDICATIONS AND USAGE section below.
Used for
From the label: indicationsSymptomatic Trichomoniasis. Metronidazole tablets are indicated for the treatment of T. vaginalis infection in females and males when the presence of the trichomonad has been confirmed by appropriate laboratory procedures (wet smears and/or cultures). Asymptomatic Trichomoniasis. […]
On the market
- Earliest approval on file
- July 18, 1963
- Generic labelers
- 55 labelers
- Pharmacy cost
- $0.102 per tablet
Supply and safety
- Shortage
- In shortage
- Recalls
- 7
Highlights of the cephalexin record
Cephalexin (Keflex) · label of December 31, 2020
Used for
From the label: indicationsCephalexin is a cephalosporin antibacterial drug indicated for the treatment of the following infections caused by susceptible isolates of designated bacteria: Respiratory tract infection ( 1.1 ) Otitis media ( 1.2 ) Skin and skin structure infections ( 1.3 ) Bone infections ( 1.4 ) Genitourinary tract infections ( 1.5 ) To reduce the development of drug-resistant bacteria and maintain the effectiveness of […]
On the market
- Earliest approval on file
- January 4, 1971
- Generic labelers
- 35 labelers
- Pharmacy cost
- $0.120 per capsule
Supply and safety
- Shortage
- No current entry
- Recalls
- 22
Source: FDA drug labels via openFDA (Metronidazole label of September 3, 2024, Cephalexin label of December 31, 2020); NDC Directory, Drugs@FDA, NADAC, FDA shortages and recalls (October 8, 2026)
How do metronidazole and cephalexin differ on the record?
In FDA's classes, metronidazole is a nitroimidazole antimicrobial and cephalexin a cephalosporin antibacterial.
Only the metronidazole label carries a boxed warning.
Generics: metronidazole since 1984; cephalexin since 1976 (Drugs@FDA).
| Metronidazole | Cephalexin | |
|---|---|---|
| Labeled for | Bacterial infections | Bacterial infections, Urinary tract infections |
| Pharmacologic class | Nitroimidazole Antimicrobial | Cephalosporin Antibacterial |
| How it works (label) | n/a | Cephalexin is a cephalosporin antibacterial drug [see Microbiology ( 12.4 )]. |
| Half-life (label) | The elimination half-life, measured during the first 3 days of life, was inversely related to gestational age. | n/a |
| Earliest approval on file (Drugs@FDA) | July 18, 1963 | January 4, 1971 |
| First generic approved | December 6, 1984 | April 26, 1976 |
| Generic labelers (NDC) | 55 labelers | 35 labelers |
| Pharmacy cost (NADAC, each one's most listed form; strengths differ) | $0.102 per tablet (Metronidazole 250 mg tablet) | $0.120 per capsule (Cephalexin 500 mg capsule) |
| 12-month price change | +10% | -6% |
| Boxed warning | Yes | No |
| Shortage now | In shortage | No current entry |
| Recalls recorded | 7 | 22 |
| FAERS reports (a report is not proof of cause; counts follow how widely a medicine is used) | 63,553 | 21,515 |
| DEA schedule | none | none |
Source: Drugs@FDA, FDA NDC Directory, CMS NADAC of October 7, 2026, FDA shortages and recalls, FAERS via openFDA (FDA files October 8, 2026)
What next?
- Alternatives to metronidazole
- every medicine labeled for the same conditions